1. Field of the Invention
The present invention relates in general to a wireless communications network that offers different services in different zones thereof. More specifically, the present invention relates to preventing toggling between the different zones of the wireless communications network.
2. Description of the Related Art
FIG. 1 is a schematic view of a conventional wireless communications network. The network shown in FIG. 1 has zone A and zone B. Each of the circles in FIG. 1 represents a cell. A zone can be made up of one or more cells. The zones are differentiated based on the services offered. For example, zone A may be a home zone to users residing therein. Within the home zone, the user may be given a more favorable calling rate or the user may be given more features in the home zone. The system shown in FIG. 1 may be implemented in a single network having different tiers of services. The planned Tiered Services in CDMA 2000 networks is one example of different tiers of services.
When the user travels between the cells shown in FIG. 1, the mobile unit must change the cell with which it is communicating. This is done in a xe2x80x9chand-off.xe2x80x9d The mobile unit is designed to operate on the cell having the strongest signal. In the overlapping areas in FIG. 1, communication is available on more than one cell. Changing signal strength in the overlapping areas can result in multiple hand-offs between cells at the boundary thereof. Signal strength changes occur due to movement of the mobile unit itself and due to movement of objects between the mobile unit and the associated cell sites. Multiple hand-offs are generally not a matter that concerns the user.
The shaded portion of FIG. 1, where zone A overlaps zone B, represents an area where communication is available on either zone A cells or zone B cells. If multiple hand-offs cause the mobile unit to toggle back and forth between cells of different zones, the user""s service is changing, and this creates problems for the user. For example, in the process of dialing a phone number to be called, at the beginning of the dialing sequence, the user may be within zone A. At this point, the user may be entitled to a free call and may not be required to dial the complete phone number, including area code. However, after the user inputs the full dialing sequence, the mobile unit may have switched to zone B. Not only will the user be forced to pay a higher rate, but the user""s call may not go through because the user did not dial the complete phone number, including area code.
Accordingly, it is an object of the present invention to prevent a mobile unit from toggling back and forth between different zones of a wireless communications network.
This and other objects are accomplished by a providing a method and device for preventing toggling between two zones of a wireless communications network. The method and device employ first and second adjacent cells respectively offering services of first and second different zones. The mobile unit determines if the second zone is more preferable than the first zone when the mobile unit hands off from the first cell to the second cell. If the second zone is less preferable than the first zone, the mobile unit does not switch to the second zone within the second cell. If the second zone is more preferable, the first zone is maintained within the second cell until the signal strength of the second cell exceeds the signal strength of the first cell by an amount determined by an exit parameter. At this point, the mobile unit switches to the services of the second zone.
Alternatively, after the mobile unit enters the second cell from the first cell, the mobile unit may be prevented from using services of the second zone if there is a hysteresis parameter associated with the second zone in the second cell and the mobile unit was not using services of the second zone in the first cell, before entering the second cell. Even if there is a hysteresis parameter associated with the second zone in the second cell, the mobile unit may be permitted to power up in the second cell on the second zone.